After three decades of searching, scientists have finally identified the source, which triggers the enzyme that helps plants resist diseases (Photo: Photo courtesy of Shutterstock)

Like animals and human beings, plants too have an immune response system, which protects them from disease causing pathogens. For many years, scientists have been studying the mechanism, which enables plants to put up a resistance against infectious parasites. But now, after three decades of searching, scientists have identified the source, which triggers the enzyme that helps plants resist diseases, according to a press release Wednesday.

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The research was a collaboration between scientists from The Sainsbury Laboratory, Norwich and RIKEN in Yokohama, Japan. Their work was published in the journal Molecular Cell. This research is a huge step towards identifying and eliminating plant pathogens that cause untold damage to crops each year. "The insights will open up new ways to improve disease resistance and stress tolerance in plants," said Professor Cyril Zipfel of The Sainsbury Laboratory, according to the release.

NAPDH oxidase RBOHD (Nicotinamide adenine dinucleotide phosphate oxidase respiratory burst oxidase homolog D) is the enzyme that triggers the immune response in plants. But what activates the NAPDH oxidase RBOHD enzyme? Scientists have now discovered that the protein BIK1 (BOTRYTIS-INDUCED KINASE1 ) activates this enzyme to mount an immune response against a perceived threat. When a pathogen attacks a plant, the protein activates the enzyme. The enzyme in turn triggers a rapid generation of signaling molecules derived from oxygen. This signaling system then triggers the formation of reactive oxygen species (ROS) that prevents the spread of the pathogen to other parts of the plant.

Discovery of the protein is a huge step for scientists who have been searching for that missing link, which triggers the enzyme to start the signaling system. "Understanding how this enzyme was rapidly activated was an important missing link in our knowledge of plant immunity," said Professor Zipfel.

Apart from being activated when attacked by pathogens, the enzyme is also triggered in response to other stress such as mechanical wounding and unfavorable environmental conditions like extreme cold or heat. The scientists also discovered that NAPDH oxidase RBOHD is regulated by biochemical processes, some of which are calcium-dependent and some of which are not.

"Our findings lay the ground for future research investigating how these processes interact and how they switch on and off the molecules essential to defence and stress responses."